JP3337339B2 - Apparatus for estimating intake air amount of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for estimating the amount of air taken into an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, there has been proposed a method of applying a fluid dynamic model to an intake system of an internal combustion engine and estimating a correct cylinder intake air amount by a model formula. The applicant of the present application also disclosed in JP-A-6-74076 that the throttle valve was regarded as an orifice and the amount of air passing through the throttle was determined from the differential pressure across the throttle valve using the principle formula of a throttle type flow rate. A method to calculate the cylinder intake air volume based on the above was proposed.

[0003] It is extremely important how to reduce the error between the cylinder intake air amount obtained from this model and the actual cylinder intake air amount. In order to improve this point, the present applicant has assumed a fluid dynamics model, but does not require complicated calculations, absorbs the errors of the model formulas, and makes the engine operation transient state, deterioration, variation, aging, etc. To eliminate
A method for more accurately estimating the cylinder intake air amount has been proposed (Japanese Patent Application No. 5-208835).

[0004]

All of these proposed cylinder intake air amount estimation methods are methods for estimating the cylinder intake air amount based on the opening degree of a throttle valve. On the other hand, due to factors such as engine vibrations being applied to the throttle body, the opening of the throttle valve may change slightly even in a steady operation state. In such a case, if the opening degree of the throttle valve is given as a change, the process of estimating the cylinder intake air amount according to this change is performed, and despite the steady operation state, The actual driving condition was not stable, and was one of the factors that reduced the driver's rally. Moreover, the relationship between the opening degree θTH of the throttle valve (butterfly valve) and the intake air amount Gc is as shown in FIG. 17, particularly when the opening degree of the throttle valve slightly changes on the low opening side. Then, the estimation process is performed on the assumption that the intake air amount Gc has greatly fluctuated. Therefore, especially when the throttle valve is on the low opening side, it is necessary to more stably perform the estimation procedure.

Accordingly, an object of the present invention is to provide an intake air amount estimating apparatus for an internal combustion engine which can stabilize a running state during a steady operation state without lowering the accuracy of an intake air amount estimating process. It is in.

[0006]

Therefore, an apparatus for estimating an intake air amount of an internal combustion engine according to the present invention has an engine speed Ne,
First means for detecting the operating state of the internal combustion engine, including the throttle opening θTH and the chamber pressure Pb, and at least the engine speed Ne and the chamber pressure Pb detected by the first means. A second means for obtaining an intake air amount Gc 'into the combustion chamber in a steady operation state; and a first throttle valve based on at least the throttle opening .theta.TH and the chamber pressure Pb detected by the first means. A third means for obtaining an effective opening area A; a first order delay value of the first effective opening area A of the throttle;
Fourth means for defining the effective opening area ADELAY, fifth means for determining the ratio of the first effective opening area A to the second effective opening area ADELAY, and defining this value as the effective opening area ratio RATIO-A of the throttle, By correcting the intake air amount Gc 'based on the effective opening area ratio RATIO-A of the throttle obtained by the fifth means, the actual intake air amount Gc can be calculated as Gc = Gc' × RATIO
In the apparatus for estimating the intake air amount of an internal combustion engine provided with the sixth means for determining as -A, when the operation state of the internal combustion engine is within a predetermined range, it is determined that the operation state of the internal combustion engine is a steady state. When the operating state of the internal combustion engine is determined to be a steady state by the steady state determining means to be considered, and the steady state determining means, the effective opening area ratio of the throttle RATIO
And a converting means for converting the value of -A into a predetermined value and providing this value to the sixth means.

According to a second aspect of the present invention, there is provided a device for estimating an intake air amount of an internal combustion engine, wherein the steady state determining means according to the first aspect determines whether the amount of change in the throttle opening within a predetermined time is:
When it is within a predetermined range, the internal combustion engine is configured to determine that the operating state is a steady state.

According to a third aspect of the present invention, there is provided an apparatus for estimating an intake air amount of an internal combustion engine, wherein the steady state determining means according to the first aspect comprises a throttle effective opening area ratio determined by a fifth means.
When the value of RATIO-A is within a predetermined range near 1, the means is configured to determine that the operation state of the internal combustion engine is a steady state.

According to a fourth aspect of the present invention, there is provided an apparatus for estimating an intake air amount of an internal combustion engine, wherein the steady state determining means according to the first aspect is configured such that a change amount of the chamber pressure Pb within a predetermined time is within a predetermined range. , The operation state of the internal combustion engine is determined to be a steady state.

[0010]

In the intake air amount estimating apparatus for an internal combustion engine according to the first aspect, the steady state determining means determines that the internal combustion engine is in a steady state when the operating state is within a predetermined range. If the steady state is determined, the value of the effective opening area ratio RATIO-A is converted to a predetermined value by the conversion means. As a result, even if the value of the effective aperture area ratio RATIO-A fluctuates slightly due to the influence of noise, etc., the effective aperture area ratio RATIO-A is maintained at a constant value during the period considered as a steady state. You.

If the amount of change in the throttle opening is substantially constant, it can be considered that the operating state of the internal combustion engine is in a steady state. Therefore, the steady state determining means according to claim 2 determines that the operating state of the internal combustion engine is in a steady state when the amount of change in the throttle opening within a predetermined time is within a predetermined range. .

Further, the value of the first effective opening area A of the throttle is the second effective opening area ADELAY at which this first-order lag value is obtained.
When it substantially coincides with, it can be considered that the operating state of the internal combustion engine is in a steady state with little change during this period. Therefore, the steady state determining means according to claim 3 determines that the operating state of the internal combustion engine is a steady state when the value of the effective opening area ratio RATIO-A is a value within a predetermined range near 1. did.

Further, even when the change amount of the chamber pressure Pb within a predetermined time is within a predetermined range,
It can be considered that the actual intake air amount Gc is substantially constant and the operation state of the internal combustion engine is in a steady state. Therefore, the steady state determining means determines that the operating state of the internal combustion engine is a steady state when the variation of the chamber pressure Pb within a predetermined time is within a predetermined range. And

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 denotes a four-cylinder internal combustion engine, and the intake air introduced from an air cleaner 14 disposed at the tip of an intake passage 12 is controlled by a throttle valve 16 in a surge tank. The fuel flows into the first to fourth cylinders via the intake manifold 20 and the intake manifold 20. An injector 2 is provided near an intake valve (not shown) of each cylinder.
2 is provided, from which fuel is injected. An air-fuel mixture in which the injected fuel and the intake air are integrated is ignited by an ignition plug in each cylinder and burned to drive a piston of the internal combustion engine. The exhaust gas after the combustion is discharged to an exhaust manifold 24 through an exhaust valve, and the exhaust pipe 2
The exhaust gas is purified by the three-way catalytic converter 28 and exhausted outside the engine.

A crank angle sensor 34 for detecting a crank angle position of a piston is provided in a distributor (not shown) of the internal combustion engine. In addition, a throttle for detecting an opening degree θ TH of the throttle valve 16 is provided. An opening degree sensor 36 and an intake pressure sensor 38 for detecting the intake pressure (chamber pressure) Pb downstream of the throttle valve 16 as an absolute pressure are also provided. An atmospheric pressure sensor 40 for detecting the atmospheric pressure Pa, an intake air temperature sensor 42 for detecting the temperature TA of the intake air, and a humidity sensor 44 for detecting the humidity of the intake air are provided upstream of the throttle valve 16. . Further, the intake passage 12 is provided with a bypass passage 32 for adjusting the amount of secondary air, which bypasses an intake passage before and after the throttle valve 16. By driving the solenoid valve 90, the bypass passage 32 is provided. Open and close. In the exhaust system, a wide-range air-fuel ratio 46 including an oxygen concentration detecting element is provided downstream of the exhaust manifold 24 and upstream of the three-way catalytic converter 28, and detects the air-fuel ratio of the exhaust gas. Outputs of these sensors 34 and the like are output from the control unit 5.
Sent to 0.

FIG. 2 shows details of the control unit. The output of the wide-range air-fuel ratio sensor 46 is input to the detection circuit 52, and the air-fuel ratio A / F is detected. The output of the detection circuit 52 is A /
The CPU 56, the ROM 58, and the R
The data is taken into the microcomputer constituted by the AM 60 and stored in the RAM 60. Similarly, the analog output of the throttle opening sensor 36 and the like is
2, multiplexer 64 and second A / D conversion circuit 66
Through the microcomputer. The output of the crank angle sensor 34 is supplied to a waveform shaping circuit 68.
After the waveform is shaped, the output value is counted by the counter 70, and the count value is input into the microcomputer. In the microcomputer, the CPU 56 calculates a control value, which will be described later, according to a command stored in the ROM 58, and drives the injector 22 of each cylinder via the drive circuit 72.

Here, the basic principle of the method of estimating the intake air amount using the fluid dynamic model adopted in the present embodiment will be schematically described (see Japanese Patent Application No. 6-197,238).
issue).

According to this method, the behavior of air in an intake system of an internal combustion engine is modeled by a physical equation (FIG. 3), and based on an air amount Gth passing through a throttle and an air amount Gb charged into a chamber, an in-cylinder air amount is calculated. This is a method for estimating the amount of intake air (actual intake air amount) Gc to be taken into the engine. Here, the "chamber" includes not only a part corresponding to a so-called surge tank but also all parts through which air flows between a throttle and an intake port serving as an inlet of a cylinder, and an effective volume actually acting as a chamber. Shall mean.

First, as shown in FIG. 4, a projection area S of the throttle (a projection area of the throttle in the longitudinal direction of the intake pipe) S is obtained from the throttle opening θTH in accordance with preset characteristics. On the other hand, as shown in FIG.
The coefficient C (the product of the flow rate coefficient α and the gas expansion correction coefficient ε) is obtained according to another characteristic set for the pressure and the intake pressure (in-chamber pressure) Pb. In the so-called throttle full-open range, the throttle does not function as a throttle, so the throttle full-open range is obtained as a critical value for each engine speed, and when the detected throttle opening exceeds this critical value, This critical value is defined as the throttle opening.

Next, the amount of air Gb in the chamber is determined from the equation (1) based on the equation of state of gas, and the amount of air ΔGb filled in the chamber this time is determined from the pressure change ΔP in the chamber according to the equation (2). Assuming that the amount of air filled in the chamber this time is not naturally taken into the cylinder combustion chamber, the amount of intake air Gc per unit time ΔT is
It can be expressed as in Equation 3.

[0022]

(Equation 1)

[0023]

(Equation 2)

[0024]

(Equation 3)

On the other hand, as shown in FIG. 6, the above-mentioned ROM 58 stores the fuel injection amount Timap in the steady operation state in accordance with the so-called speed density method.
Is set in advance so as to be searchable from the data and the intake pressure Pb. Further, since the fuel injection amount Timap searched here is set according to the target air-fuel ratio A / F determined according to the engine speed Ne and the intake pressure Pb, as shown in FIG. Basic value of air-fuel ratio A / F KB
S is also mapped and stored in advance so that it can be freely searched from the engine speed Ne and the intake pressure Pb. The fuel injection amount Timap is set so as to satisfy the steady-state operation state in the aforementioned fluid dynamics model. The valve opening time of the injector 22 is set directly as a unit.

Here, under certain conditions in a steady operation state (conditions defined by the engine speed Ne1 and the intake pressure Pb1), the fuel injection amount Timap1 determined by the map search is as shown in the following equation (4). .

[0027]

(Equation 4)

By preparing this map value so as to satisfy the above-described model equation, the fuel injection amount Timap1 'in the steady operation state, which is determined based on the fluid dynamics model, is determined.
Naturally coincides with the fuel injection amount Timap1 determined by the map search.

On the other hand, the fuel injection amount Timap1 'in the steady operation state and the fuel injection amount Timap2' in the transient operation state, which are determined based on the fluid dynamics model, are obtained by setting the target air-fuel ratio to the stoichiometric air-fuel ratio (14.7: Assuming 1), it is expressed by Expression 5 and Expression 6.

[0030]

(Equation 5)

[0031]

(Equation 6)

In both equations, when comparing the throttle passing air amount Gth1 in the steady operation state and the throttle passing air amount Gth2 in the transient operation state, only the effective opening areas A1 and A of the throttle are different. Therefore, the throttle-passing air amount Gth2 in the transient operation state can be expressed by Expression 7.

[0033]

(Equation 7)

By using the ratio between the effective opening area of the throttle valve in the steady state and the effective opening area of the throttle valve in the transient state based on the equations (3) and (7), the throttle-passing air amount Gth1 in the steady state is calculated. In addition, the throttle passing air amount Gth2 in the transient operation state can be expressed.

Further, assuming that the current effective opening area of the throttle valve is A and the effective opening area of the throttle valve in the steady operation state is A1, the effective opening area A1 of the throttle valve in the steady operation state is the current throttle opening area. It can be grasped as a first-order delay of the effective opening area A of the valve (FIG. 8). That is, if the first-order lag of A is called "ADELAY", it is understood that A1 and ADELAY have substantially the same value. Therefore, when approximating a model using the concept of a fluid dynamic model, A / (first order delay of A) may be used.

As shown in FIG. 9, in the transient operation state, at the moment when the throttle is opened, the pressure difference before and after the throttle is large, so that the amount of air passing through the throttle flows at a stretch and gradually falls to a steady state. The throttle passing air amount Gth in the state can be expressed by the ratio A / ADELAY. In the steady operation state, this value is "1" as shown in the lower graph of FIG. Hereinafter, this ratio is referred to as "RATI
OA ".

The effective opening area of the throttle largely depends on the throttle opening, and changes substantially following the change in the throttle opening (FIG. 10). Therefore, the above-described first-order lag value of the effective opening area is treated equivalently to the first-order lag value of the throttle opening. Further, in order to eliminate the delay in which the chamber filling air amount ΔGb is reflected on the intake air amount Gc, the first order delay of the value ΔGb is considered in addition to the first order delay of the throttle opening.

Thus, by calculating the chamber filling air amount Gb from the throttle passing air amount Gth, the intake air amount Gc can be obtained based on the throttle passing air amount Gth. This simplifies the configuration and reduces the amount of calculation. Specifically, the intake air amount Gc per unit time ΔT can be expressed as in Expression 8.
Also, when Expressions 9 and 10 are expressed in the form of a transfer function,
Equation 11 is derived. As shown in equation (11), the intake air amount Gc can be obtained from the primary delay value of the throttle passing air amount Gth.

[0039]

(Equation 8)

[0040]

(Equation 9)

[0041]

(Equation 10)

[0042]

[Equation 11]

FIG. 11 is a block diagram showing a series of such arithmetic processing. Since the intake air amount Gc can be handled in the same manner as the fuel injection amount, in the following block diagrams and the like, the intake air amount is handled as the fuel injection amount for convenience. In the figure, "(1-
B) / (z−B) ”means a first-order lag in a discrete transfer function.

Therefore, under certain conditions in a steady operation state (conditions defined by the engine speed Ne and the intake pressure Pb)
When the fuel injection amount determined by the map search is described as Timap, the fuel injection amount Tout to be actually output is determined by the following equation. Tout = Timap × RATIO-A Here, the arithmetic processing performed by the intake air amount estimating apparatus in the present embodiment is
FIG. 12 is a block diagram.

As described above, when the operating state of the engine is in the steady state, the influence of the detected noise is removed.
It is necessary to stabilize the operation of estimating the intake air amount. Therefore, in the estimating apparatus according to the present embodiment, the steady state determining unit 100 that determines whether the operating state of the engine is the steady state, and the steady state determining unit 100 determines that the operating state of the engine is the steady state. In this case, a conversion unit 101 that converts the value of the effective aperture area ratio RATIO-A of the throttle into a predetermined value is provided.

Hereinafter, the operation of the intake air amount estimating apparatus will be described with reference to the main flowchart of FIG. This flowchart is started at each TDC position.

First, the engine speed N detected by each sensor
e, intake pressure Pb, throttle opening θTH, pressure Pa, engine cooling water temperature Tw, etc. are read (S10). The throttle opening θTH learns the fully closed throttle opening in the idling operation state and uses the learned value.

Next, it is determined whether or not the engine is being cranked (started) (S20). If it is determined that cranking is being performed ("YES" in S20), a predetermined table (not shown) is searched from the water temperature Tw to calculate the fuel injection amount Ticr during cranking (S21), and then the start mode The fuel injection amount Tout is determined on the basis of the equation (not described) (S22).

On the other hand, if it is determined in S20 that cranking is not being performed ("NO" in S20), subsequently, it is determined whether or not fuel cut is performed (S30). If it is determined that the fuel is cut ("YE" in S30)
S "), the fuel injection amount Tout is set to zero (S31).

If "NO" is determined in S30,
ROM 5 based on engine speed Ne and intake pressure Pb
8 (FIG. 6), the fuel injection amount Timap in the steady operation state (the intake air amount G in the steady operation state).
c ′) is obtained (S40). Retrieved fuel injection amount Timap
Thereafter, pressure correction and the like are appropriately added as necessary (not shown).

Next, the throttle opening θ TH read in S10 and the first-order lag transfer function “(1-B) / (z−
B), a first order delay value θTH-D of the throttle opening is calculated (S50). Next, based on the throttle opening θTH and the intake pressure Pb, the current effective opening area A of the throttle is calculated by the above-described method (S60). Next, the primary delay value θTH-D of the throttle opening and the intake pressure Pb
The first order delay value ADELA of the effective opening area of the throttle
Y is calculated (S70).

Next, "RATIO-A" is calculated from the following equation: RATIO-A = (A + ABYPASS) / (A + ABYPASS) DELAY (S80). ABYPASS means the amount of air (shown as “lift amount” in FIG. 12) that is drawn into each cylinder combustion chamber via the bypass passage 32 without passing through the throttle valve. In order to determine the amount, it is necessary to consider this amount of air, and therefore, the calculation is performed in consideration of this amount of air. Specifically, a value corresponding to the air amount is converted into a throttle opening ABYPASS in accordance with a predetermined characteristic, obtained and added to the effective opening area A, and the sum (A + ABYPASS) and an approximation of the first order delay are obtained. A ratio with the value “(A + ABYPASS) DELAY” is obtained, and is set as RATIO-A.

As described above, as a result of addition to both the numerator and the denominator, even if there is an error in the measurement of the amount of air taken into each cylinder combustion chamber without passing through the throttle valve, the measured fuel injection amount is not increased. Impact is reduced.

Subsequently, it is determined whether or not the operating state of the engine is a steady state (S90). Here, a specific method of determining the steady state is shown in the flowchart of FIG. First, assuming that the throttle opening obtained at the current timing synchronized with TDC is θTH (k) and the throttle opening obtained at the previous timing is θTH (k−1),
By calculating (k) -θTH (k-1), a change amount ΔθTH of the throttle opening θTH during this period is obtained (S9).
1). Next, if the absolute value of the obtained change amount ΔθTH is within the predetermined steady state determination value ΔθCHK, the operating state of the engine is determined to be in the steady state, and the steady state determination value ΔθCHK
If the value exceeds the threshold value, it is determined that the operating state of the engine is in a transient state (S92). Note that the throttle opening θ
Since the relationship between TH and the intake air amount Gc is the relationship shown in FIG. 17, based on this characteristic, the steady-state determination value Δθ CHK becomes
For example, on the low opening side, it is desirable to set to about 0.5 deg. In addition, as shown in the graph of FIG. 15, it is desirable to set individually according to the throttle opening θTH.
In this setting, the value of the steady-state determination value ΔθCHK for each throttle opening θTH is stored in advance in the ROM 58 or the like, and the value of the steady-state determination value ΔθCHK is read according to the throttle opening θTH at that time.

Subsequently, if the operating state of the engine is determined to be a transient state ("NO" in S90), the RATIO-G obtained in S80 is added to the Timap (Gc ') obtained by searching in S40.
A is multiplied by A to calculate a fuel injection amount Tout (Gc) corresponding to the amount of air passing through the throttle (S110).

On the other hand, if it is determined that the operating state of the engine is a steady state ("YES" in S90), conversion unit 10
In step 1, the value of RATIO-A obtained in S80 is replaced with a preset value "1.0" (S100). Then, based on this value, in S110, the fuel injection amount Tout (G
c) is calculated. In this case, the fuel injection amount Tout (Gc)
Becomes equal to Timap (Gc ').

As described above, the change amount Δθ of the throttle opening is
When the TH is within a certain small range, by performing arithmetic processing assuming that the operating state of the engine is in a steady state, it is possible to remove the influence of detected noise etc. and stabilize the intake air amount estimation processing operation be able to.

In the present embodiment, the determination as to whether or not the operating state of the engine is in the steady state is made based on the variation ΔθTH of the throttle opening θTH.
It is also possible to determine whether the operating state of the engine is in a steady state.

For example, S90 in the flowchart of FIG.
In the above, the steady state of the engine may be determined based on the value of the throttle effective opening area ratio RATIO-A obtained in S80. In this case, if the value of RATIO-A is "1.00", the value of the effective opening area A of the throttle is equal to the first-order lag value ADELAY. In this case, the operating state of the engine is steady. It can be determined that it is in the state. In addition, considering the influence of the vibration of the engine which causes noise as described above, if the value of RATIO-A is in the range of 0.95 to 1.05, for example, the operating state of the engine Can be considered as a steady state. Therefore, the value of RATIO-A is 0.95
If it is within the range of 1.05, it is determined that the vehicle is in a steady state ("YES" in S90), and in S100, the value of RATIO-A is newly set to "1.00".

In this setting process, the value of RATIO-A can be replaced with the converted value of RATIO-A according to the characteristic determined by the characteristic line 1 shown in FIG.

In addition, all of these exemplified methods of determining the steady state of the engine are processings performed based on the detected value of the throttle opening θTH. The detection can also determine the operating state of the engine. Specifically, the intake pressure Pb is detected in synchronization with the TDC, and the difference (absolute value) between the detected values obtained at the previous time and the present time is a value within the range of the predetermined steady-state determination value ΔPbCHK. If this is the case, the operating state of this engine is determined to be a steady state.

It is desirable that the value of the steady-state determination value ΔPbCHK be set in advance corresponding to each engine speed Ne in the same manner as described above (FIG. 18). For example, in the idle state,
If the fluctuation of the intake pressure Pb is within the range of ± 20 mmHg, it is determined that the operating state of the engine is in a steady state (S90).
Then, a process of resetting the value of RATIO-A to "1.00" is performed (S100).

In this determination process, the value of the steady-state determination value ΔPbCHK with respect to the engine speed Ne is determined in advance by RO
It is desirable that the value of the steady-state determination value ΔPbCHK be read in accordance with the engine speed Ne at that time during the determination process.

In the embodiment described above, the fuel injection amount Tim
Although the example in which ap is mapped in advance has been shown, instead of this, the intake air amount Gc 'in the steady operation state is mapped,
It may be stored in the ROM 58.

In this embodiment, the conversion unit 101 converts the value of the effective opening area ratio RATIO-A of the throttle to "1.00" when the operating state is in a steady state. The present invention is not limited to the example.
It is also possible to set an arbitrary value near 1.00, such as “2”.

Further, in the illustrated embodiment, the fuel injection amount is determined in accordance with the estimated intake air amount. However, the present invention is not limited to this example. Other engine control parameters such as an ignition timing and an exhaust gas recirculation amount (EGR amount) can be calculated according to the intake air amount.

[0067]

As described above, in the internal combustion engine intake air amount estimating apparatus according to the first aspect of the present invention, the steady state determining means determines whether the operating state of the internal combustion engine is in the steady state during the conversion. By means, the effective opening area ratio R
A configuration that converts the value of ATIO-A to a predetermined value was adopted.
Therefore, effective aperture area ratio RAT
Even if the value of IO-A fluctuates somewhat, the effective opening area ratio RATIO-A is maintained at a constant value during the period considered as a steady state, so the process of estimating the intake air amount must be stabilized. Can be.

In the apparatus for estimating the amount of intake air for an internal combustion engine according to the second aspect, the steady state determining means determines that the engine is in a steady state if the amount of change in the throttle opening is within a predetermined range. . Therefore, even when the throttle opening is detected to be slightly fluctuated in spite of a steady state due to, for example, vibration of the engine applied to the throttle body, this fluctuation may be within the predetermined fluctuation range. For example, it can be regarded as a steady state, and subsequent estimation processing can be performed. Therefore, the process of estimating the intake air amount in the steady state can be stabilized.

Further, in the intake air amount estimating apparatus for an internal combustion engine according to the third aspect, the value of the first effective opening area A of the throttle is the second effective opening area ADELAY which becomes the first order delay value.
, The effective aperture area ratio RATIO
The case where the value of -A is within a predetermined range near 1 is determined to be a steady state by the steady state determining means. Therefore,
Since the first effective opening area A and the like of the throttle are obtained based on the value of the throttle opening, even when the detected throttle opening contains a little noise or the like in spite of the steady state, The subsequent estimation process can be performed assuming that it is in the steady state.

Further, in the intake air amount estimating device for an internal combustion engine according to the fourth aspect, it is possible to determine whether the operating state is a steady state or not by the amount of change in the chamber pressure Pb. A configuration including a steady state determining means for determining a steady state based on the condition is adopted. Therefore,
If the variation of the chamber pressure Pb is within a predetermined range,
Even if the throttle opening can be determined to be in a steady state regardless of the throttle opening and the detected throttle opening contains noise or the like,
The subsequent estimation processing can be performed assuming that it is in a steady state. As a result, the process of estimating the intake air amount in the steady state can be stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an arrangement position of an internal combustion engine and various sensors according to an embodiment;

FIG. 2 is a block diagram showing a configuration of a control device in the intake air amount estimating device for the internal combustion engine.

FIG. 3 is an explanatory diagram showing a fluid dynamic model adopted in the present embodiment.

4 is a block diagram showing a method of calculating an effective opening area of a throttle valve using a flow coefficient or the like using the fluid dynamic model of FIG. 3;

FIG. 5 is an explanatory diagram showing map characteristics of coefficients used in the calculation of FIG. 4;

FIG. 6 is an explanatory diagram showing a map characteristic of a fuel injection amount in a steady operation state.

FIG. 7 is an explanatory diagram showing a map of a target air-fuel ratio.

FIG. 8 is a data diagram showing a simulation result of an effective opening area of a throttle.

FIG. 9 is an explanatory diagram showing a steady operation state and a transient operation state in this embodiment.

FIG. 10 is an explanatory diagram showing a relationship between a throttle opening and an effective opening area of a throttle.

FIG. 11 is a block diagram illustrating a calculation process of a fuel injection amount (intake air amount).

FIG. 12 is a block diagram showing a calculation process of a fuel injection amount (intake air amount).

FIG. 13 is a main flowchart showing a calculation process of a fuel injection amount (intake air amount).

FIG. 14 is a flowchart showing the operation of S in the main flowchart of FIG. 13;
9 is a flowchart illustrating a determination process performed at 90.

FIG. 15 is a graph showing a relationship between a throttle opening and a steady state determination value.

FIG. 16 is a graph used when converting the value of RATIO-A.

FIG. 17 is a graph showing a relationship between a throttle opening and an intake air amount.

FIG. 18 is a graph showing a relationship between an intake pressure and a steady state determination value.

[Explanation of symbols]

10 internal combustion engine, 12 intake path, 16 throttle valve,
20: intake manifold, 34: crank angle sensor, 36: throttle opening sensor, 38: intake pressure sensor, 100: steady state determination unit, 101: conversion unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-42600 (JP, A) JP-A-6-74076 (JP, A) JP-A-62-206245 (JP, A) 18638 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-45/00 F02D 13/00-28/00

Claims (4)

(57) [Claims] 1. A first means for detecting an operating state of an internal combustion engine including an engine speed Ne, a throttle opening .theta.TH, and a chamber pressure Pb, and at least the engine speed detected by the first means. A second calculation of the intake air amount Gc 'into the combustion chamber in the steady operation state based on the number Ne and the chamber pressure Pb.
Means for obtaining a first effective opening area A of the throttle based on at least the throttle opening θTH detected by the first means and the chamber pressure Pb; Fourth means for obtaining a first-order lag value of the first effective opening area A and setting the value as a second effective opening area ADELAY of a throttle; and a ratio of the first effective opening area A to the second effective opening area ADELAY. Fifth means for obtaining the value of the effective opening area ratio RATIO-A of the throttle, and the intake air amount based on the effective opening area ratio RATIO-A of the throttle obtained by the fifth means. By correcting Gc ′, an intake air amount estimating apparatus for an internal combustion engine comprising: a sixth means for obtaining the actual intake air amount Gc as Gc = Gc ′ × RATIO-A. When within the predetermined range,
A steady state determining means for assuming that the operating state of the internal combustion engine is in a steady state; and, if the operating state of the internal combustion engine is determined to be in a steady state by the steady state determining means, an effective opening area ratio of the throttle -Convert the value of A to a predetermined value,
Conversion means for giving the value to the sixth means. An intake air amount estimating apparatus for an internal combustion engine, comprising: 2. The steady state determining means determines that the operating state of the internal combustion engine is a steady state when the amount of change in the throttle opening within a predetermined time is within a predetermined range. Claim 1 characterized by the following:
An intake air amount estimating device for an internal combustion engine according to any one of the preceding claims. 3. The operating state of the internal combustion engine when the value of the effective opening area ratio RATIO-A obtained by the fifth means is within a predetermined range near 1. 2. The apparatus for estimating an intake air amount of an internal combustion engine according to claim 1, wherein it is determined that is in a steady state. 4. The steady state determining means determines that the operating state of the internal combustion engine is in a steady state when the variation in the chamber pressure Pb within a predetermined time is within a predetermined range. The intake air amount estimation device for an internal combustion engine according to claim 1, wherein: